The present invention relates to a servo arrangement, especially for brake force amplifiers for automotive vehicles with a power take-off means and drive means, preferably operated by muscle power, and connected with the power take-off means by elastically deformable connecting means, in which an auxiliary moment provided by a servomotor is transmitted over a coil spring coupling to the power take-off means by means of a coil spring coupling in dependence on the deformation of the elastically deformable connecting means.
In a known servo arrangement of this kind, the coil spring coupling is constituted by coil spring in which, in order to render the coupling active, the coil spring is expanded. While this construction operates satisfactorily, it is relatively large and complicated. This may render, especially when the servo arrangement is to be used in automotive vehicles as brake force amplifiers, the known construction unsuitable for use.